Add extracted source directory and README navigation

extracted-source/node_modules/is-stream/index.js

@@ -0,0 +1,29 @@
+export function isStream(stream) {
+	return stream !== null
+		&& typeof stream === 'object'
+		&& typeof stream.pipe === 'function';
+}
+
+export function isWritableStream(stream) {
+	return isStream(stream)
+		&& stream.writable !== false
+		&& typeof stream._write === 'function'
+		&& typeof stream._writableState === 'object';
+}
+
+export function isReadableStream(stream) {
+	return isStream(stream)
+		&& stream.readable !== false
+		&& typeof stream._read === 'function'
+		&& typeof stream._readableState === 'object';
+}
+
+export function isDuplexStream(stream) {
+	return isWritableStream(stream)
+		&& isReadableStream(stream);
+}
+
+export function isTransformStream(stream) {
+	return isDuplexStream(stream)
+		&& typeof stream._transform === 'function';
+}